Light and electron microscopic preparations of biopsy cores from sensori-motor cortex of awake cats will be examined in order to identify horseradish peroxidase (HRP)-injected, physiologically recorded neurons. This procedure will be used to relate the intracellular physiology of a neuron to its morphology. Preliminary ultrastructural studies of biopsy cores from cerebellum have shown adequate preservation of HRP-injected neurons and surrounding neuropil. The success of these studies indicate that this method can be applied to the cerebral cortex. The first series of planned experiments will be involved with confirming for the cat sensorimotor cortex the known neuronal types within cerebral cortex. This objective involves the determination of the presence of the three general categories of cortical neurons, pyramidal, aspinous stellate and spinous stellate cells. In the second series of proposed experiments, I will examine HRP-injected cortical neurons in both light and electron microscopic preparations. A vigorous analysis of ultrastructural morphology will be made for each neuron, and the emphasis will be placed on reconstructing parts of somata and dendrites from serial thin sections. Following the morphological identification of these neurons, attempts will be made to correlate intracellular recordings with each neuronal type. The significance of this proposed project is that it will allow a direct relationship to be drawn between the physiology and morphology of individual cortical neurons in awake cats. It is anticipated that such information will provide a better understanding of cortical functioning in both normal and altered states.